With recent developments in laser technology and its application in ophthalmology, laser surgery has become the technique of choice for ophthalmic surgery, including refractive surgery for correcting myopia, hyperopia, astigmatism, and the like, and cataract surgery for treating and removing a cataractic lens. Laser eye procedures employ different types of laser beams, such as an ultraviolet laser, an infrared laser, or a near infrared, ultra-short pulsed laser. The surgery is typically performed while the patient is in a reclined position but fully awake. As such, the patient's eye movement has to be stabilized during surgery to ensure the procedure's accuracy and efficacy.
There are various ways to stabilize a patient's eye movement. One approach has the patient focusing on a visual fixation target during the procedure. These targets typically include a light emitting diode (LED), which is optically positioned in front of or above the patient within his or her line of vision. The fixation system generally keeps the LED in focus for the patient even though the optical characteristics of the patient's eye are changing during surgery. Viewing the fixation light targets allows the patient to maintain a steady eye position, thus reducing random eye movement. Exemplary systems and methods for visual fixation are described in U.S. Pat. Nos. 6,004,313 and 6,406,473, issued to Shimmick et al., and U.S. Pat. No. 6,793,654, issued to Lemberg, which are incorporated here by reference in their entirety.
One challenge with contemporary visual fixation systems is that when the surgeon views an image of the patient's eye on a video microscope's LCD display, he or she sees interference in the image caused by light reflections from the fixation system's intervening optics and the cornea. During surgery, surgeons typically rely on the image of the eye captured by a video microscope's LCD display. Light reflection from the visual fixation target, however, often creates a haze in the middle of the displayed image, thereby degrading the quality of the live video feed. This is particularly undesirable for surgeons who depend on a precise image of the eye for the laser treatment.
Hence, improved systems and methods for visual fixation and image display during a laser ophthalmic surgery and/or an ophthalmic diagnostic procedure are desirable.